This invention relates to high performance passenger tires and, more particularly, to belted radial pneumatic tires with improved bead assemblies suited for use on high performance automobiles with atypically high speed capability.
There are vehicles, principally automobiles, available presently which are designed, engineered, and manufactured to perform at atypically high speeds. Some of these high performance automobiles are capable of operation at speeds in excess of 130 mph (210 km/hr). Manufacturers, drivers, and passengers of these high performance automobiles have come to expect that certain of the principal parts or accessories for these automobiles, such as tires, be suitable for or compatible with the high speed capability of such automobiles.
To fulfill these expectations, tire manufacturers are now designing, engineering, and manufacturing tires to be particularly suited for use on such high performance automobiles. Some of these tires carry "speed-ratings" to indicate their suitability for particular types of vehicles. For example, tires are now produced for the consumer market with a speed rating of "V" indicating a suitability for or compatibility with certain types of sports cars, luxury touring automobiles, and law enforcement pursuit vehicles with top speed capabilities over 130 mph (210 km/hr).
One goal of ongoing high performance tire development is to evolve toward advanced tire constructions which further improve performance properties such as safety, comfort and high speed capabilities in excess of minimum V-rated speeds without disrupting the overall balance of handling characteristics. Such advanced tire must, therefore, necessarily possess many construction, compound, and design features which may compromise the desired handling characteristics of the tire.
It has long been recognized that the use of advanced construction features such as reinforcements in the bead areas can improve the performance of pneumatic tires. Examples of such reinforcements can be found in U.S. Pat. Nos. 2,493,614 and 3,253,639. These patents recognize and discuss the problems of radial and circumferential deformations in the bead assemblies of tires which result in shear stresses during operation and use of such tires. However, in both of these patents, the concern is with larger, heavy-duty, low speed truck tires which are subjected to operating conditions which are very severe, but very different from the conditions encountered in the smaller, high speed automobile tires of the present invention. The improvements described in these patents are clearly different in structure including construction and placement within the tire from the improvements of the present invention. The improvements in the bead assemblies as described in the prior patents are also clearly different in function since the present invention is directed to a tire for use with high speed automobiles rather than a tire for use with low speed trucks.
A belted radial pneumatic tire constructed for high speed and superior handling characteristics in which the bead assemblies of the present invention could be readily utilized is disclosed in U.S. patent application Ser. No. 669,163 entitled HIGH PERFORMANCE TIRE, filed Nov. 7, 1984, and assigned to the assignee of the present invention. According to the disclosure of that patent application, an annular belt assembly utilizes folded belt plies in association with pairs of narrow superposed strips overlying the folds at the margins of the folded belt plies. The utilization of such folded belt plies, along with the associated excess cost of materials, has been found unnecessary to achieve the superior results capable when used in combination with the bead assemblies constructed in accordance with the teachings of the present invention.
A tire with bead assemblies constructed in accordance with the teachings of the present invention has been found to improve all significant performance properties including handling characteristics such as braking, steering response, swingout, plowing, lift throttle oversteer, and cornering stability. These handling characteristics were subjectively graded in the conventional fashion by an expert jury navigating, under controlled conditions, either a road course or an autocross course. Such improvements in handling characteristics are possible due to new design features in the bead assemblies, an area of a tire which must be designed, engineered, and manufactured with great attention. The construction of the bead assemblies is recognized to be among the most critical areas for superior tire performance and user safety.